Hydrogenase from Rhizobium japonicum bacteriods is being investigated by kinetic analysis to establish the mechanism of its action. A comparative study of HD formation by nitrogenase from several bacteria is being made to establish whether the process of HD formation is uniform among nitrogen fixers. Formation of complexes between nitrogenase components and the Shethna iron protein II is being studied and tests will be made of the effectiveness of the complex to protect nitrogenase against inactivation by O2. The possible role of superoxide dismutase in O2 protection also is under review. The activating factor for dinitrogenase reductase from Rhodospirillum rubrum is being purified so that its properties and mode of action can be established.